A Real-World FFT Example

Figure 1: Shown at top right is the output of a
5V switch-mode power supply acquired
with an RP4030 active voltage-rail probe

Performing a fast Fourier transfer (FFT) on an oscilloscope can be likened to driving a car. Just as there are two dominant strains of power-train transmissions, there are two dominant approaches to transferring signals acquired on an oscilloscope from the time domain to the frequency domain. There's the stickshift approach, in which the FFT parameters are set manually, and the automatic approach, in which you let the oscilloscope make decisions for you.